On the Nature of the T Tauri Triple System

Abstract

We present a multi-wavelength analysis to reveal the nature of the enigmatic T Tauri triple star system. New optical and infrared measurements are coupled with archival X-ray, UV and mm datasets to show morphologies of disk material and outflow kinematics. A dark lane of obscuring material is seen in silhouette in several emission lines and in model-subtracted ALMA mm continuum dust residuals near the position of T Tau Sa+Sb, revealing the attenuating circumbinary ring around T Tau S. The flux variability of T Tau S is linked in part to the binary orbit; T Tau Sb brightens near orbital apastron as it emerges from behind circumbinary material. Outflow diagnostics confirm that T Tau N powers the blue-shifted western outflow, and the T Tau S binary drives the northwest-southeastern flow. Analysis of the southern outflow shows periodic arcs ejected from the T Tau system. Correlation of these arc locations and tangential kinematics with the orbit timing suggests that launch of the last four southern outflow ejections is contemporaneous with, and perhaps triggered by, the T Tau Sa+Sb binary periastron passage. We present a geometry of the T Tau triple that has the southern components foreground to T Tau N, obscured by a circumbinary ring, with mis-aligned disks and interacting outflows. Particularly, a wind from T Tauri Sa that is perpendicular to its circumstellar disk might interact with the circumbinary material, which may explain conflicting high contrast measurements of the system outflows in the literature. T Tauri is an important laboratory to understand early dynamical processes in young multiple systems. We discuss the historical and future characteristics of the system in this context.

ALMA Super-resolution Imaging of T Tau: r = 12 au Gap in the Compact Dust Disk around T Tau N

“…Hence, these sizes should be considered to be the conservative upper limits. The total flux density of T Tau Sb is a factor of seven smaller than T Tau Sa, which is in good agreement with a factor of eight given in Beck et al (2020). This implies that the actual disk size of T Tau Sb would be about three times smaller than that of T Tau Sa when we consider the scaling relation between the mm-continuum disk radii R mm and luminosities L mm ; L mm ∝ R 2 mm (Tripathi et al 2017;Andrews et al 2018a;Hendler et al 2020).…”

“…We reanalyzed the ALMA archival data obtained for T Tau on August 18, 2017, as part of the project 2016.1.01164.S (PI: Herczeg), including the continuum at 225.5 GHz and 13 CO (J = 2−1) and C 18 O (J = 2−1) line data. Continuum data have already been published in Long et al (2019); Manara et al (2019); Beck et al (2020). The observations were performed with a 12-m array consisting of forty-three 12-m antennas (C40-7 antenna configuration with the baseline length extending from 21.0 m to 3637.7 m) and the on-source time of the target source was 8 min.…”

“…Here, we investigate the global disk properties of T Tau N derived from the SpM image and compare them with previous studies based on mid-infrared and millimeter observations. The T Tau N disk is known to be viewed as nearly face-on (Akeson et al 1998;Ratzka et al 2009;Long et al 2019;Manara et al 2019;Beck et al 2020). We derived the inclination and PA of the disk on the image by fitting an ellipse to the outer ring, as described in Appendix D. As shown in Table 3.3, the measured inclination of 25.2 ± 1.1 • agrees well with < 30 • derived from mid-infrared interferometric observations with very large telescope interferometer (VLTI) and SED simulations (Ratzka et al 2009) as well as with 28 • from visibility fitting using the same ALMA data (Manara et al 2019;Beck et al 2020).…”

“…This system consists of a star (T Tau N) in the north and a close binary (T Tau Sa and Sb) in the south (Dyck et al 1982;Koresko 2000), located in the Taurus star-forming region at a distance of 143.7 ± 1.2 pc, as measured by Gaia DR2 (Gaia Collaboration et al 2016Collaboration et al , 2018. Both T Tau N and T Tau S (Sa + Sb) are embedded in an infalling envelop (Momose et al 1996), jets have been found to associated with both sources (Beck et al 2020). T Tau N is classified as Class II, while T Tau S is a Class I system (Furlan et al 2006;Luhman et al 2010).…”

A triple star in disarray

“…These values are compatible with the orbit prediction within the error bars if T Tauri S previously went through the ascending node. Since then, T Tauri S has been moving behind T Tauri N for about 80 years and would now be located roughly 90 AU behind T Tauri N. However, the N-S orbit is still only loosely constrained and orbital solutions may exist for which T Tauri S is located in front of T Tauri N, as suggested by Beck et al (2020).…”